Tests helpful in making a diagnosis

The main value of blood tests in the assessment of someone with possible ME/CFS is to exclude other common conditions which produce fatigue as a principle symptom. This means the following tests should always be considered before a diagnosis is confirmed; these can be arranged by your GP if she/he is agreeable:

• anaemia
  People with ME/CFS do not have anaemia as part of this illness. If the haemoglobin level is reduced, then an alternative explanation should always be pursued.
• white cell count
  A measurement of the number of cells which fight off infection. This count is often increased during the early stages of an infection but as ME/CFS becomes chronic, the level usually starts to return to normal. Some people with ME/CFS have abnormally shaped white cells (atypical lymphocytes), particularly following glandular fever. A raised level of a type of white cell known as eosinophils can occur with allergies or when infection with toxocara is present (the latter should always be queried when a child has eosinophilia).
• ESR or acute phase protein changes (e.g.CRP)
  The ESR test is a useful indicator of general health. If raised, this suggests some form of chronic infection or inflammation is present. The vast majority of people with ME/CFS have a normal ESR.
• liver, thyroid and kidney function tests
  Liver function tests are sometimes abnormal in ME/CFS. This may be due to the precipitating infection causing liver inflammation or the effects of antidepressant drugs. There is also a condition called Gilbert's disease which seems to be more common in people with ME/CFS (ref: Lancet, 1993, 341, 842 and 1162-1163). If liver tests remain abnormal then further investigation may be warranted. There is no evidence that hormonal disturbances in ME/CFS involve the thyroid gland: the results of thyroid function tests should always be normal.
• routine biochemistry (urea, electrolytes, calcium etc.)
  results should all be within the normal range. A raised level of blood calcium could be due to sarcoidosis. A lowered level may indicate osteomalacia (a bone disease causing fatigue and bone pain). Research from Australia indicates that the total amount of body potassium may be lowered in ME/CFS (ref: Medical Journal of Australia, 1996, 164, 384). A raised level of potassium can occur in Addison's disease.
• creatine kinase
• urine tests for sugar/protein
• hormone levels
  In some cases, investigations should also include checking female hormone levels (serum oestradiol) and adrenal gland function.

Other blood tests which could be considered will depend on specific symptoms. For example, if irritable bowel symptoms are experienced then checking for adult-onset coeliac disease would be worthwhile, particularly if the symptoms appear to be relieved by a wheat-free diet.

A number of research studies have now reported on characteristic abnormalities in certain hormones (e.g. cortisol, prolactin and arginine vasopressin) which come under the control of a part of the brain known as the hypothalamus. However, these results are not consistently abnormal in all ME/CFS patients. Neither are the tests readily available outside research units.

Blood flow scans of the brain (SPECT scans) have produced interesting results (i.e. brain stem hypoperfusion) which appear to be almost unique to ME/CFS, but these are not widely available. Blood flow abnormalities in the brain stem will need to be confirmed by other research groups before they can be considered as a useful diagnostic aid.